In order to preserve non-liquid food products (i.e.; vegetables or pieces of meat), sensitive to oxygen, it is known to package said food products in a packaging with a low oxygen content.
In the case of packaging that is substantially dimensionally stable, such as for example metal tins filled in limited juice, the reduction in the oxygen content is obtained primarily by placing the metal tin in a vacuum. Possibly, a non-oxidising gas (i.e. N2) sweeps the products in order to remove the residual oxygen.
The tin is then closed with a lid which is crimped in a vacuum. In order to substantially reduce the quantity of oxygen, this method requires machine speeds that are relatively low, much less than conventional industrial speeds (400 cpm).
Another disadvantage of this method resides in the fact that the packaging must be sufficiently resistant to mechanically resist a vacuum. In the case of metal tins, it is as such required to provide tin thicknesses at least equal to 0.18 mm in order to prevent said tin from imploding. Another disadvantage of this method is the difficulty in obtaining residual oxygen contents that can be reproduced.
For the case of a packaging (metal tin) with limited headspace, i.e. comprising a low volume of air in the vicinity of the opening because it is practically entirely filled with a juice, another method of inerting consists in blowing a non-oxidising gas (i.e. N2) on said headspace, and simultaneously closing and crimping the lid. This method however consumes a substantial amount of non-oxidising gas and is therefore expensive.